Project Summary Prostate cancer (PCa) has surpassed lung cancer as the leading cancer among American men. The majority of patients have already developed metastatic lesions at initial clinical presentation and androgen ablation has become a standard therapy because PCa is an androgen-dependent (AD) disease. Inevitably, the recurrence of castration resistant PCa (CRPC) will result in mortality of patients since CRPC cells are resistant to conventional chemotherapy. Moreover, because of high age, PCa patients often do not have favorable physical conditions to tolerate undesirable side effects of chemotherapy. Thus, developing a new, safe and effective therapy becomes a high priority. Although PCa patient survival with newly developed therapeutic regimens has been significantly improved, PCa remains incurable. One of the possible theories to explain the recurrence and ineffectiveness of cancer treatment is the cancer stem cell (CSC) model in which a subset of tumor cells is responsible for cancer initiation and progression as well as cancer recurrence. These CSCs share with normal stem cells the properties of self-renewal, immortal and differentiation into a variety of cell types including heterogeneous lineages of cancer cells. Also, CSC can re-grow from a few cells left behind after therapy, it will be important to develop therapies that are more specifically directed against CSCs. Thus, targeting cancer stem cell is now becomes an active research area of cancer therapy to achieve the ultimate cure. In order to target PCa specifically, we are developing a new biodegradable and biocompatible nanoparticle that can target PCa specifically with imaging capabilities. Using this unique delivery system, we propose to engineer a unique genotoxin that can preferentially kill PCa cells expressing stem cell properties then evaluate the therapeutic efficacy of PCa monitored by molecular imaging in pre-clinical animal models. We expect be able to monitor the drug delivery and/or response of cancer cells in a real-time manner. This experimental therapy could become a better regimen for treating CRPC because this agent has a PCa specificity, which is expected to be less toxic than chemotherapeutic agents. Most importantly, this proposal is to explore a new avenue of tailored therapy in contrast to conventional therapeutic strategy; we expect that the outcome of this study should have an immediate clinical impact on CRPC therapy.